Fire resistant textile material

ABSTRACT

A fire resistant textile material comprising a fire resistant textile material comprising a woven face fabric composed of fibres selected from: meta-aramid, para-aramid, polyamideimide and mixtures thereof; wherein the number of warp face threads, per unit width (cm) is greater than the number of weft threads, per unit length (cm).

This invention relates to fire resistant textile materials and garmentsmade from these materials. The invention relates particularly but notexclusively to articles of clothing for use by fire fighters and fortextiles for manufacture of such clothing.

European legislation requires employers to provide garments whichprotect their employees against hazards to which they may be exposed.Clothing for protection against heat and flame must pass minimumperformance requirements for flame, radiant heat, heat resistance,tensile and tear strength, abrasion resistance and penetration by waterand liquid chemicals. The assembled garments must achieve levels ofresistance to heat transfer by both flame and radiant heat.

One of the most effective ways to reduce second and third degree burnsis to make sure that the barrier of protective clothing between the heatsource and the skin remains intact during exposure. This property isreferred to as the break open resistance or non-break open protection ofthe fabric.

Outer textile materials for fire fighting clothing have previously beenmanufactured from 100% meta-aramid or polyamideimide, blends ofpolyparaphenylene isophthalamide (meta-aramid e.g. Nomex) andpolyphenylene terephthalamide copolymer (para-aramid fibres e.g. Kevlar)or by use of core spun yarns or staple mixtures with polyparaphenyleneterephthalamide copolymer or fibres comprising para-aramid cores withmeta-aramid or polyamideimide covers. The combination of these fibres inthe fabric enhances the non-break open protection of the product.However meta-aramid and para-aramid fibres shrink, consolidate andthicken when exposed to a high temperature heat source. The presence ofmeta-aramid or para-aramid in either the fibre blend or as a core can beused to prevent fibre shrinkage and consequent breaking open of thegarment. However the inclusion of para-aramid fibre in the blend hasbeen found to be insufficient in tightly woven fabrics to preventbreaking open. Consequently there is a need for improved textilematerials for manufacture of fire fighting garments and the like.

Fire fighting garments have been made from a plurality of textilelayers, including an outer layer of woven meta-aramid fibre, for exampleas manufactured under the trade mark Nomex. Break open protection may beafforded by blending with para-aramid fibres, for example asmanufactured under the trade mark Kevlar and as disclosed in U.S. Pat.Nos. 3,063,966 and 3,506,990. However charring of such blends may leadto cracking and embrittlement with consequent deterioration of physicalproperties.

EP 1173635 discloses a fire resistant textile material comprising awoven faced or warp knitted fabric composed of meta-aramid, para-aramidor mixtures thereof, the fabric including a woven mesh back oflow-thermal shrinkage fibres which form an interwoven backing scrim onthe face of the fabric, the ratio of face to back yarns being in therange of 6:1 to 12:1.

According to a first aspect of the present invention a fire resistanttextile material comprises a woven face fabric composed of fibresselected from: meta-aramid, para-aramid, polyamideimide and mixturesthereof; wherein the fabric comprises face warp threads and back warpthreads, wherein the number of face warp threads per unit width (cm) isgreater than the number of weft threads per unit length (cm).

The face warp threads may be incorporated meta-aramid fibres or blendsof fibres including meta-aramid fibres, particularly including more than50% w/w meta-aramid fibres. Exemplary fibres provide good abrasionresistance, having an extension to break value of 10% or greater,preferably 15% or greater.

When meta aramid face warp fibres are used the proportion of meta-aramidfibres may be equal or greater than 90%, for example greater than 93%,for example greater than 95%. The back warp fibres may be selected frompara-aramid fibres and blends including para-aramid, particularlyincluding more than 50% para-aramid. Exemplary fibres provide good breakopen resistance.

When polybenzimidazole [PBI] or a high para-aramid content face warp isused advantageous abrasion resistance of the face warp threads may beprovided by incorporation of a blend including a proportion, for exampleup to 10% w/w of polyamide (Nylon®) or by use of a blend of polyamidewith up to 5% w/w antistatic fibres, for example fibres comprising acarbon core and a polyamide sheath.

The face warp may already comprise stretch broken para-aramid fibres; ora blend of stretch broken para-aramid and polybenzimidazole [PBI],polyetheretherketone, high tenacity viscose or carbon fibres. Back warpthreads comprising para-aramid or PBI provide high thermal stability andmay have a count finer, that is lighter in weight than 60/2 Nm.Relatively fine yarns having a count greater than 60/2 Nm may beemployed.

A back warp yarn having high break open resistance as disclosed abovemay be stitched onto the back of the woven face fabric. Where blendedfibres are used these may be spun into a yarn.

The back warp yarn may have a count greater than (that is finer orlighter in weight) than 60/2 Nm. Therefore the face warp yarn may becoarse (that is heavier) than the back warp yarn and may have a countof, for example, 40/2 Nm.

The proportion and count of face side yarns to reverse side yarns may bedetermined by-the required weight of the final fabric, the interlacingof the face weave and the degree of effectiveness required from theproperties of the reverse side yarn.

The weft yarn may conveniently comprise fibres which are the same as theback warp fibres.

Fabrics in accordance with the invention may confer the advantage ofincreased thermal protection together with greater flexibility incomparison to traditional single layer fabrics of comparable weights.

Fabrics of this invention may serve to increase the thermal protectionafforded by the garment and may increase the number of seconds needed toraise the temperature on the inner side to a level which would createpain or a second degree burn on human skin or on the type of sensor usedin Thermal Protection Procedure (TPP) testing.

The presence of low thermal shrinkage fibres on the surface of agarment, for example Kevlar may result in formation of fine fibrils, dueto abrasion in use. Coloured fabrics, for example dark blue fabrics asused for fire fighters' tunics may therefore develop light specks on thesurface of the fabric. This gives an uneven appearance on a darkcoloured garment. This effect is referred to as fabric frosting.

Fire resistant fabrics in accordance with this invention confer afurther advantage in comparison to fabrics constructed in a traditionalmanner, by packing the face of the fabric with threads that exhibitreduced liability to abrasion. Also as described above, by facilitationof the selection of yarn constructed from blends of fibres that improvethe abrasion resistance.

The low shrinkage fibres are preferably located behind the face fabric.This minimises exposure of the strengthening fibres to the heat source.

Fabrics in accordance with this invention may be produced byinterweaving yarns which have been spun, plied or core spun from staplefibres and/or multifilament fibres which may comprise 100% meta-aramid,100% para-aramid, 100% polyamide imide or intimate blends of anycombination of these fibres.

In a preferred method the yarns for the warps of both the face andreverse sides of the fabric may be assembled in the specifiedproportions and order of working by the sectional warping process ontoone or two warped beams jointly having the total number of ends requiredto weave the final fabric.

The weft yarns may be inserted across and interlaced with the warp yarnsin the specified proportions, order of working and density selected toproduce the required face and reverse side weaves.

Differential tension may be applied to the face and reverse side yarnsduring the weaving process and during the insertion of the weft. This isimportant to compensate for the varying degrees of elongation which areinherent in the different types of fibres used in those yarns and whichare important to the properties of the fabric of this invention.

A preferred weaving machine which may be used to produce a fabric ofthis invention will supply the face and back warp yarns from individualwarp beams at different feed rates to compensate for the varying degreesof elongation and the varying inter-lacings of the face fabric yarns andreverse side yarns.

Previously known firelighters' garments comprise composites of threetextile layers: an outer fabric, a moisture barrier and a quiltedthermal lining. The present invention may reduce the need for use ofsuch layers or may allow the weight of the layers to be reduced.

The fabric may have a warp back construction. This construction allowsfor a relatively fine face appearance with to the additional fabricthickness due to the extra back warp threads.

The additional thickness may give improved thermal properties incomparison to an equivalent single fabric.

Fabrics of this invention may have a lighter weight whilst providing ahigh degree of thermal protection, flexibility and durability allowingcomfortable use in a wide range of protective garments.

The flexibility is enhanced through the structure by packing the facewith fibres/yarns arranged in one direction i.e. the warp direction andloosely interlacing the weft direction with the back warp where thepacking/density/set of the weave is lower.

Fabrics of this invention may have a lighter weight while providing ahigh degree of thermal protection, flexibility and durability includinghigh abrasion resistance and stability to multiple washing cycles, whilegiving comparable or superior performance than heavier weight fabricscurrently in the market place. The lighter weight fabrics of thisinvention may also reduce heat stress experienced by a wearer and maycontribute to reduction in overall weight of the garment.

Fabrics in accordance with this invention may have a gaberdine faceeffect. Gaberdine is a fabric having a surplus of ends over picks. Inexemplary gaberdine fabrics the excess of ends to picks may be in therange of 1.25:1 to 2:1 although the range may vary dependent on therequired fabric weight and yarn count used.

Exemplary fabrics of this invention may have a weave structure selectedfrom: 2×1 twill or 2×1 twill with rip stop.

A 2×1 twill is a weave comprising units in which each warp thread passesover two weft threads then under one weft thread, successive units beingoffset by one weft interlaced thread.

Further advantageous fabrics of this invention include 2×2 twill, 3×1twill, 3×1 satin weave, end warp satin weave, 3×1 Broken Crow, Devon,Venetian, Doeskin and the like; all of the aforementioned fabrics beingeither with or without rip stop.

The ratio of face warp yarns to back warp yarns may be in the range fromabout 1:1 to 20:1, for example about 1:1 to about 16:1, for exampleabout 1:1 to about 15:1.

The proportion of face ends to back ends may be in the ratio of 5:1.

Alternative ratios may be selected from 1F (face) to 1B (back), 2F to1B, 4F to 1B, 7F to 1B, 8F to 1B, 10F to 1B, 11F to 1B, 13F to 1B, 14Fto 1B, 16F to 1B, 17F to 1B, 19F to 1B, or 20F to 1B.

An increased ratio of ends to picks may give a steep twill appearance tothe finished cloth. This may improve runoff of water or other liquids inuse.

In contrast to a conventional warp back construction, each back end maybe interlaced with a weft pick. This has the advantage that if the facewarp is stripped from the fabric in use, the back warp and weft maycontinue to form a loosely woven fabric.

Preferably the face:back ratios which are divisible by the repeat numberof face ends in the weave are avoided.

In an exemplary embodiment the repeat number of face ends is 3. In thiscase proportions of 3F (face) to 1B (back), 6F to 1B, 9F to 1B, 12F to1B, 15F to 1B and 18F to 1B are not used.

Use of a warp back stitched to the weft increases the weight of thefabric while maintaining the fineness of the face. The back warp yarnand weft may be selected from para-aramid, PBI or blends thereof, theback warp being interlaced with every thread of the weft. This has theadvantage that there are no loose yarns which may burn away when exposedto a high level of heat.

The yarns employed in a fabric of this invention may be selected to haveweft tensile and tear strengths sufficient to meet the requirements foruse in a specific fabric with a relatively reduced number of picks perunit measure.

For example the weft yarn may be selected from: (1) a relatively highstrength, Nm50/1 (Numerometric, including single or multiple folding ofyarns) 100% para-aramid yarn or (2) a combination of Nm50/1 and Nm 50/2100% para-aramid yarns with Nm20/2 or (3) Nm 50/1 with Nm40/2meta-aramid yarns.

According to a second aspect of this invention there is provided afirefighter's garment comprising a textile material in accordance withthe first aspect of this invention. Garments in accordance with thisinvention are advantageous in comparison to previously known garments.

The invention is further described by means of an example, but not inany limitative sense, with reference to the accompanying drawings ofwhich:

FIG. 1 illustrates a first fabric in accordance with this invention;

FIG. 2 illustrates the second fabric in accordance with this invention;

FIG. 3 illustrates the third fabric in accordance with this invention;and

FIG. 4 illustrates a fourth fabric in accordance with this invention.

FIG. 1 is a diagram showing a fabric in accordance with this inventionin which face warp threads A interlace with weft threads C to form a 2×1twill gaberdine effect face

to the cloth. Back warp threads B interlace with weft threads C but hangon the back of the cloth, unseen on the face adding bulk and weight tothe fabric.

FIG. 2 is a diagram showing a fabric in accordance with this inventionin which face warp threads A interlace with weft threads C and D to forma 2×1 rip stop twill gaberdine effect face to the cloth. Back warpthreads B interlace with weft threads C and D but hang on the back ofthe cloth, unseen on the face adding bulk and weight to the fabric.

FIG. 3 is a diagram showing a fabric in accordance with this inventionin which a face warp threads A interlace with weft threads C and E toform a 2×1 twill gaberdine effect face to the cloth. Back warp threads Binterlace with weft threads C and E but hang on the back of the cloth,unseen on the face adding bulk and weight to the fabric.

FIG. 4 is a diagram showing a fabric in accordance with this inventionin which a face warp threads A interlace with weft threads C, D and F toform a 2×1 rip stop twill gaberdine effect face to the cloth. Back warpthreads B interlace with weft threads C, D and F but hang on the back ofthe cloth, unseen on the face adding bulk and weight to the fabric.

1. A fire resistant textile material comprises a woven face fabriccomposed of fibres selected from: meta-aramid, para-aramid,polyamideimide and mixtures thereof; wherein the fabric comprises facewarp threads and back warp threads, wherein the number of face warpthreads per unit width is greater than the number of weft threads perunit length.
 2. A fire resistant textile material as claimed in claim 1,wherein the face warp threads are selected from meta-aramid fibresincluding more than 50% meta-aramid fibres.
 3. A fire resistant textilematerial as claimed in claim 1 wherein the warp face threads comprise ablend of meta-aramid fibres with up to 10% w/w polyamide fibres or 10%w/w of a blend of polyamide with up to 5% w/w antistatic fibres.
 4. Afire resistant textile material as claimed in claim 3 wherein the facewarp threads comprise a proportion of meta-aramid fibres equal orgreater than 90%, for example greater than 93%, for example greater than95%.
 5. A fire resistant textile material as claimed in claim 4 whereinthe back warp fibres are selected from para-aramid fibre blendsincluding more than 50% para-aramid fibres.
 6. A fire resistant textilematerial as claimed in claim 5 wherein the face warp threads comprise:stretch broken para-aramid fibres or a blend of stretch brokenpara-aramid and polybenzymidazole (PBI), polyetherketone, high-tenacityviscose or carbon fibres.
 7. A fire resistant textile material asclaimed in claim 6 in the back warp fibres comprising para-aramid or PBIhave a count finer than 60/2 Nm.
 8. A fire resistant textile material asclaimed in claim 1, wherein the face of the fabric contains abrasionresistant fibres.
 9. A fire resistant textile material as claimed inclaim 1, wherein low shrinkage fibres are located behind the facefabric.
 10. A fire resistant textile material as claimed in claim 1,having a gaberdine face effect.
 11. A fire resistant textile material asclaimed in claim 10 wherein the excess of face warp yarns to weft yarnsis in the range of 1.25:1 to 2:1.
 12. A fire resistant textile materialas claimed in claim 1, wherein the fabric is a 2×1 twill or 2×1 twillwith rip stop.
 13. A fire resistant textile material as claimed in claim1, wherein the fabric is selected from: 2×2 twill, 3×1 twill, 3×1 satinweave, end warp satin weave, 3×1 Broken Crow, Devon and Venetian andDoeskin; all of the aforementioned fabrics being either with or withoutrip stop.
 14. A fire resistant textile material as claimed in claim 1,wherein the ratio of face warp yarns to back warp yarns is in the rangefrom 1:1 to 20:1.
 15. A fire resistant textile material as claimed inclaim 14, wherein the ratio of face warp yarns to back warp yarns is inthe range of 1:1 to 16:1.
 16. A fire resistant textile material asclaimed in claim 15, wherein the ratio of face warp yarns to back warpyarns is in the range of 1:1 to 15:1.
 17. A fire resistant textilematerial as claimed in claim 1, wherein the ratio of face ends to backends is 5:1.
 18. A fire resistant textile material as claimed in claim17, wherein the ratio is selected from 1F (face) to 1B (back), 2F to 1B,4F to 1B, 7F to 1B, 8F to 1B, 1° F. to 1B, 11F to 1B, 13F to 1B, 14F to1B, 16F to 1B, 17F to 1B, 19F to 1B, or 20F to 1B.
 19. A fire resistanttextile material as claimed in claim 1, wherein each back end isinterlaced with a weft pick.
 20. A firefighter's garment comprising atextile material in accordance with claim 1.